The present invention relates to screw heads of the type described in U.S. Pat. No. 4,084,478 dated Apr. 18, 1978, as generally shown in FIGS. 2 and 3 thereof. Such screw heads are provided with ribs on some of the driver-engageable surfaces of the head to interlock with an edge of the driver to reduce the tendency for the driver to slip out of engagement with the screw head during driving and removal.
In producing such ribs with a metal punch, the metal of the screw head tends to flow outwardly from the screw axis as well as axially, and accordingly, may not completely fill in the rib during the head forming operation.